3 Spectrum Analyzer Mode
3.2 Swept SA Measurement
If the instrument is in Single sweep, and not Averaging/Holding, and you want to
take one more sweep, press Restart.
If the instrument is in Single sweep, and Averaging/Holding, and you want to take
one more sweep without resetting the Average trace or count, go to Meas Setup and
increment the average count by 1 by pressing the Step-Up key while Average/Hold
Num is the active function. You can also do this by sending :CALC:AVER:TCON UP.
Sweep Time Annotation
Lets you specify whether you want to see, for Sweep Time, an estimate of the total
time the instrument is taking to make a sweep, or 1/(Sweep Rate) as has
traditionally been the case.
In previous instruments, Sweep Time has always been displayed, when taking a
sweep by the swept method (as opposed to the FFT method), as 1/(Sweep Rate),
even though that may be shorter than the time it actually takes to perform a sweep.
This value of 1/(Sweep Rate) is an excellent indication of how fast the local oscillator
is moving, and the experienced user can infer much from this quantity about the
optimal value of other settings, like Res BW.
However, 1/(Sweep Rate) can be much less than the total time it takes the
instrument to do a multi-band sweep over a wide frequency range, due to band
switching and settling times that may add to the total sweep time.
Because of this, you are now given the option of which value the instrument will
display. Sweep Time Annotation provides two choices, NORMal and ESTimated. If
you prefer the traditional method (that is, always display 1(sweep rate)), choose
Normal (1/Sweep Rate). If instead you choose Estimated, the estimated actual
sweep time is displayed, which is the time from start to finish of a sweep, as well as it
can be estimated. This is displayed in the Sweep Time annotation area and is still
called Sweep Time, as always. To show you that this is the estimated actual sweep
time instead of 1/(Sweep Rate), it is preceded by a tilde (~), so it will look like this
(for example):
Sweep ~5.3 s (1001 pts)
instead of
Sweep 440 ms (1001 pts)
Note that this value does not include the time between sweeps, so it not a measure
of “cycle time”.
Note also that Estimated Sweep Time only applies when Sweep Type = Swept; when
Sweep Type = FFT, the behavior remains as it always has for FFT sweeps, the display
is (for example):
Sweep (FFT) ~1.2 s (1001 pts)
486 Spectrum Analyzer Mode User's &Programmer's Reference
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